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FACC Frequently Asked Questions

What is the status of FACC?

What is the final version of FACC?

How are the versions of FACC documented?

How does the FACC relate to the DFDD?

How do specific items in the FACC relate to specific items in the DFDD?

What is the "FACC to DFDD Lineage Trace"?


What is the status of FACC?

DGIWG has maintained the Feature and Attribute Coding Catalogue (FACC) as a part of the DIGEST exchange standard and as part of NATO STANAG 7074. The initial version of FACC was developed together with DIGEST version 1 and the latest version was included as part of DIGEST Edition 2.1 issued in September 2000. FACC has been an important part of the standardization of geographic information for the military community by providing the common set of geographic features used in a number of products based on DIGEST.

DGIWG is preparing to retire the DIGEST exchange standard and is developing a suite of more flexible geographic information standards for military applications based on the suite of ISO/TC 211 19100 series standards. In alignment with the concepts for feature cataloguing expressed in the ISO/TC 211 standards, the new approach establishes a data dictionary of feature, attribute and enumerant concepts in a register. This data dictionary is called the DGIWG Feature Data Dictionary (DFDD). The data dictionary can be extended and maintained through a formal registration process allowing more flexibility and responsiveness than previous paper-based mechanisms. Specific dated feature catalogues can be developed for data products binding selected features, attributes and enumerants used in that particular product.

Although DIGEST remains a valid standard, part 4 (FACC) has been sunsetted by DGIWG. Sunset standards are those that have been identified and approved for retirement. Usually a pre-defined event and date are associated with the eventual retirement of the standard. In addition, a replacement standard is frequently identified. For FACC the DFDD is the replacement standard. Backward compatibility is supported since the final version of FACC was the basis for the initial contents of the DFDD register. Feature catalogues based on the DFDD will also be registered to facilitate interoperability between data products based on the DFDD.

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What is the final version of FACC?

While the final version of DIGEST is Edition 2.1 (September 2000), the FACC continued under maintenance through October 2003 in a series of revised baselines. There are four such revisions, the final being known as BL 2003-4, released October 2003.

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How are the versions of FACC documented?

FACC, along with the DIGEST, has historically been documented as a paper-based product, however in its latter years it was released as a set of Adobe Acrobat "pdf" files. Available in this format are:

These packages are "zipped" archives. Adobe Acrobat Reader is required to view the included PDF files.

Beginning with FACC 2.0 Amendment 1, the FACC was internally maintained as a Microsoft Access database through its retirement. A cumulative package of versions of that database and a supporting user interface is available as:

  • FACC Cumulative: Includes FACC Versions: 2.0 Amendment 1; 2.1; BL 2003-1; BL 2003-2; BL 2003-3; and BL 2003-4.

This package is a "zipped" archive. Microsoft Access 2000 or later is required to use its contents.

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How does the FACC relate to the DFDD?

The final version of FACC (BL 2003-4, October 2003) was the basis for the initial contents of the DGIWG FDD register. Through a "fundamental review" process the geographic information concepts specified by the FACC have been incrementally transformed into a new set of geographic information concepts with greater clarity, coherency, and consistency in specification. While efforts have been made to limit the impact on applications when transitioning from the use of the FACC to the use of the DFDD, there is impact that must be addressed.

While the DGIWG FDD both incorporates many geographic information concepts from its predecessor Feature and Attribute Coding Catalogue (FACC) and uses a similar approach to concept denotation ("coding") it does not share the same namespace (code space). In consequence, when the same code-value (for example: "GB005") happens to appear in both the FACC and the DFDD it may denote different geographic information concepts.

Therefore, when migrating legacy/heritage geographic data originally encoded using the FACC (for example: as used in the DIGEST Edition 2.1) to conform to the DFDD, it will likely be necessary to "re-code" the data. The DGIWG FDD register includes the requisite item-specific supersession information documenting these concept lineages and, where appropriate, provides data migration guidance regarding geographic information concepts included in the FACC that have been subsequently retired.

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How do specific items in the FACC relate to specific items in the DFDD?

The DFDD is maintained in accordance with ISO 19135 Geographic information—Procedures for registration of items of geographic information. ISO 19135 specifies how to organize registers as collections of registered items, identifies basic information that all registered items shall include, and provides a register item lifecycle model. The lifecycle model identifies that a register item may be Valid, Superseded, or Retired.

  • While Valid, a register item may undergo clarifications that improve the specification of the item but do not change the item semantic.
  • Changes in item semantic are accomplished by adding a new item for the changed semantic and then establishing that the new item supersedes the old item (which is accordingly no longer Valid).
  • Retiring an item identifies it as being no longer Valid, but also as not having a specific superseding item.

Throughout the "fundamental review of FACC" process this lifecycle mechanism has been used to capture lineage information as the contents of the FACC have been transformed into the contents of the DFDD. Each item in the DGIWG FDD register includes lineage information establishing its lineage to predecessor item(s) in the FACC, if any.

Lineage, however, is not the same as equality.

While the DGIWG Feature and Attribute Data (FAD) Project Team (PT) has gone to considerable lengths to honor the distinction between clarifications and supersessions, it has not been possible to draw an unambiguous boundary between the two. Accordingly while it is the case that supersessions clearly identify changes in concept meaning, it is also the case that some clarifications document item changes that may - in some contexts - be considered as changes in item meaning (semantic).

As lineage tracing is {data production, data use} context-independent, it does not necessarily result in a mapping that may be exactly applied to existing systems or data sets. This is particularly the case given that the FACC "coded attribute value" concepts did not include definitions and are well-known to have been used to mean different things at different times in different data products from different producers.

It is also true that the data types of numerous attributes have been revised, new data types introduced, and the approach to attribute value metadata rationalized and rigorously applied across all attribute concepts in the transition from FACC to the DFDD.

Finally, items in the FACC have been split, joined, and refactored in various manners to achieve a greater consistency across the DFDD.

As a consequence, while information regarding how specific items in the FACC relate to specific items in the DFDD has been maintained, this information can not be directly used as a data mapping.

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What is the "FACC to DFDD Lineage Trace"?

To assist users of DIGEST Edition 2.1 in transitioning to use of the DFDD, a lineage trace has been prepared in the form of a Microsoft Excel workbook that summarizes information from the DFDD register in a manner determined to be most useful to system engineers.

This "summary" lineage trace was established for the relationship from FACC 2.1 directly to DFDD BL 2005-2. DFDD BL 2005-2 was selected based on its use in the Multinational Geospatial Co-Production (MGCP) Technical Requirements Document (TRD) Feature Catalogue, Version 1.

In the workbook, intermediate versions of the FACC and/or DFDD (seven versions total) are skipped over and only the final end-to-end lineage captured. In consequence of this skipping, the workbook does not document all details of individual lineages - only a summary. This information was augmented by experience from members of the FAD Project Team in order to "optimize" the end-to-end summary for use by system engineers. The full lineage information is readily available in the DGIWG FDD register.

As lineage tracing is {data production, data use} context-independent, it does not necessarily result in a mapping that may be exactly applied to existing systems or data sets. Mappings can only be determined given other context information, and may be different at different times, for different systems/purposes. This workbook is merely a potentially useful reference tool for migrating existing data systems and data sets from a basis on FACC Edition 2.1 to a basis on DFDD BL 2005-2. Nothing more.

The DGIWG FAD Project Team does not certify that direct use of information incorporated into this workbook to transform either data sets or systems will result in a lossless transition from the use of the DIGEST FACC to the use of the DGIWG FDD. Data/system-specific impacts will need to be assessed by subject matter experts and engineers familiar with those specific data systems and data sets.

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